Hydrogen Evolution Reaction (HER) is a prototype simple catalytical reaction with only a few steps and species involved, nevertheless, several models have been attempted for predicting catalyst activity. This study seeks to use a data-first approach by fitting hydrogen and hydroxide adsorption energies, Delta E-H and Delta E-OH, as well as work functions obtained using DFT to experimental data and correlating the outcome models with possible mechanisms for HER in acidic and alkaline conditions. Statistical proof is given for the importance of the work function as a descriptor in both acidic and alkaline, explaining the overestimation of Cu activity by Delta E-H volcano models and predicting its overpotential required for a 1 mA cm(-2) current density correctly within 0.1 eV. An oxophobic HER pathway is identified in alkaline conditions.